The HDMI Licensing Knowledge Base is a library of current information about the HDMI standard.
Select an appropriate category from the pull down below, or, you may use your own search terms to obtain results.
If your question involves a specific product, please contact the manufacturer directly. The HDMI Knowledge Base does not contain information about specific products.
Q. Does HDMI support Closed Captioning?Close Captioning
The evolution from analog to digital TV has added some complexity to Close Captioning (CC). With one standard way of broadcasting/transmitting, decoding and displaying content NTSC or PAL, depending on region, analog TV made enabling CC fairly easy across CE devices since the TV was able to do all the CC decoding.
With the advent of digital TV and the introduction of digital HDTV services (cable, satellite, etc.) the responsibility of decoding CC has been taken away from the TVs and put into the various Set Top Boxes (STB) that are required for the majority of the digital HDTV services. Additionally, these STBs now have different ways of enabling CC making it complicated and creating confusion for consumers. All set-top boxes are required to support CC, however the implementation of CC can vary from one product to another. Enabling CC on a specific set-top box can be simple, or more difficult, depending on the implementation.
HDMI, LLC recommends contacting your TV service provider (cable, satellite, etc.) for the correct way to switch on its CC feature as a first step to resolve this issue. The second step is to contact the manufacturers directly for the correct way to enable the CC feature within your product.
HDMI and Close Captioning
Closed Captioning (CC) works differently with digital connections (HDMI, DVI, etc.)How old analog CC worked:
Source always sent CC information to the TV and the TV controlled whether the CC was displayed or not via the TV's remote (CC button). The CC button on the TV only controls CC for analog connections (S-Video, Composite, Component) or Over The Air tuners (ATSC digital or NTSC analog)
How CC works in HDMI and other digital connections:
The TV remote's CC button does not enable/disable CC on HDMI sources. To enable CC, the user must enable it at the source either through a source remote control key (i.e. CC button) or by going through the setup menu of the source. The source will then combine the video content with the CC information and output that (video + CC) via HDMI to the TV.
The CC rendering is done at the source and not at the TV as it was with analog connections. For example, with a typical cable box the CC is enable by going to the cable box setup menu and not the TV remote's CC button. The TV remote's CC only controls the analog CC and does not control the CC for each of the HDMI source devices. CC must be enabled from each of the individual HDMI sources.
Exact steps to enable CC varies between manufacturers so please contact the source manufacturer for instructions.Return to top
Q. What is HDMI technology?
HDMI (High-Definition Multimedia Interface) technology is the industry-leading interface and de-facto standard connecting high-definition (HD) and ultra high-definition (UHD) equipment, from HDTVs and personal computers to cameras, camcorders, tablets, Blu-ray players, gaming consoles, smartphones, and just about any other device capable of sending or receiving an HD signal.
Over 1,600 of the largest consumer electronics, PC and mobile device manufacturers are HDMI Adopters and over 4B HDMI-enabled devices have shipped as of 2014.
By delivering crystal-clear, all-digital audio and video via a single cable, HDMI technology dramatically simplifies cabling and helps provide consumers with the highest-quality HD experience. It transmits all ATSC HDTV standards and supports 8-channel, 192kHz, uncompressed digital audio and all currently-available compressed formats, with bandwidth to spare to accommodate future enhancements and requirements.Return to top
Q. Who supports the HDMI Interface?
The HDMI Founders include leading consumer electronics manufacturers Hitachi Maxell, Ltd; Panasonic Corporation; Koninklijke Philips Electronics N.V.; Silicon Image (a Lattice Semiconductor company); Sony Corporation; Technicolor S.A.; and Toshiba Corporation.
In addition, the HDMI interface has the support of major motion picture producers including Fox, Universal, Warner Bros. and Disney, and system operators such as DirecTV, EchoStar (Dish Network) and CableLabs.
The HDMI Specification has been licensed by over 1,600 companies, and is a standard feature in over 4B consumer products (IHS, 2014).
In 2011, the HDMI Founders created the HDMI Forum to guide future iterations of the technology, enabling companies in diverse markets to participate in the evolution of the HDMI Specification. Approximately 60 of the largest consumer electronics, PC and semiconductor companies are now working together to ensure the continued success of the HDMI Specification.Return to top
Q. What are the advantages of HDMI over existing analog video interfaces such as composite, S-Video and component video?
Quality: Because HDMI is a digital interface, it provides the best quality of the video since there are no lossy analog to digital conversions as are required for all analog connections (such as component or S-video). The difference is especially noticeable at higher resolutions such as 1080p. Digital video will be sharper than component, and eliminates the softness and ghosting found with component. Small, high contrast details such as text bring this difference out the most.
Ease-of-use: HDMI combines video and multi-channel audio into a single cable, eliminating the cost, complexity, and confusion of multiple cables currently used in A/V systems. This is particularly beneficial when equipment is being upgraded or added.
Intelligence: HDMI supports two-way communication between the video source (such as a DVD player) and the DTV, enabling new functionality such as automatic configuration and one-touch play. By using HDMI, devices automatically deliver the most effective format (e.g 480p vs 720p, 16:9 vs 4:3) for the display that it is connected to - eliminating the need for the consumer to scroll through all the format options to guess what looks best.
HD Content-Ready: HDMI devices supporting HDCP have the comfort of knowing they will have access to premium HD content now and in the future. HD-DVD and Blu-ray have delayed the activation of the image constraint token (a.k.a. content protection flag) with today’s HD movies to help minimize potential issues caused by the transition, but are expected to activate this in a few years, meaning future HD movies will then not be viewable at HD resolutions over unprotected interfaces such as analog component.Return to top
Q. What functionality was added to each version of HDMI?
The following provides an overview of major functionality added to each version of HDMI:
- Adds features and capabilities that increase HDMI's appeal for use in both the CE and PC industries. Specifically, the features and modifications for HDMI 1.2 include: Support for One Bit Audio format, such as SuperAudio CD's DSD (Direct Stream Digital), changes to offer better support for current and future PCs with HDMI outputs, including: availability of the widely-used HDMI Type A connector for PC sources and displays with full support for PC video formats, ability for PC sources to use their native RGB color space while retaining the option to support the YCbCr CE color space, requirement for HDMI 1.2 and later displays to support future low-voltage (i.e., AC-coupled) sources, such as those based on PCI Express I/O technology.
- Consumer Electronic Control (CEC) features and command sets and CEC compliance tests are now fully specified.
- Creation of version 1.2a of the HDMI Compliance Test Specification (CTS), which includes a CEC Supplement. HDMI CTS 1.2a has been updated for technical consistency with HDMI Specification 1.2a as well as to the recently released HDMI Specification 1.2.
- Significantly, CTS 1.2a contains additional cable and connector testing and Authorized Testing Center (ATC) submission requirements. Specifically, under CTS 1.2a, the Adopter shall submit for testing to the ATC any new HDMI cable whose length exceeds previously tested cables.
- Additionally, HDMI Licensing, LLC will maintain a list of approved connectors. For a device to pass CTS 1.2a testing at an ATC, all connectors on such device must appear on the approved connector list. To add a connector to this list, the vendor must submit to the ATC or HDMI Licensing, LLC full and passing testing results.
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- Higher speed: HDMI 1.3 increases its single-link bandwidth to 340 MHz (10.2 Gbps) to support the demands of future HD display devices, such as higher resolutions, Deep Color and high frame rates. In addition, built into the HDMI 1.3 specification is the technical foundation that will let future versions of HDMI reach significantly higher speeds.
- Deep Color: HDMI 1.3 supports 10-bit, 12-bit and 16-bit (RGB or YCbCr) color depths, up from the 8-bit depths in previous versions of the HDMI specification, for stunning rendering of over one billion colors in unprecedented detail.
- Broader color space: HDMI 1.3 adds support for “x.v.Color™” (which is the consumer name describing the IEC 61966-2-4 xvYCC color standard), which removes current color space limitations and enables the display of any color viewable by the human eye.
- New mini connector: With small portable devices such as HD camcorders and still cameras demanding seamless connectivity to HDTVs, HDMI 1.3 offers a new, smaller form factor connector option.
- Lip Sync: Because consumer electronics devices are using increasingly complex digital signal processing to enhance the clarity and detail of the content, synchronization of video and audio in user devices has become a greater challenge and could potentially require complex end-user adjustments. HDMI 1.3 incorporates automatic audio synching capabilities that allows devices to perform this synchronization automatically with total accuracy.
- New HD lossless audio formats: In addition to HDMI’s current ability to support high-bandwidth uncompressed digital audio and all currently-available compressed formats (such as Dolby® Digital and DTS®), HDMI 1.3 adds additional support for new lossless compressed digital audio formats Dolby TrueHD and DTS-HD Master Audio™.
Q. Are all of the new HDMI versions backward compatible with previous versions?
Yes, all HDMI versions are fully backward compatible with all previous versions.Return to top
Q. What testing is required?
Prior to mass producing or distributing any Licensed Product or component that claims compliance with the HDMI Specification (or allowing someone else to do such activities), each Adopter must test a representative sample for HDMI compliance. First, the Adopter must self test as specified in the then-current HDMI Compliance Test Specification. The HDMI Compliance Test Specification provides a suite of testing procedures, and establishes certain minimum requirements specifying how each HDMI Adopter should test Licensed Products for conformance to the HDMI Specification. Such compliance testing is limited to evaluation of a product's compliance with the HDMI Specification and is not designed to test the overall performance of any Licensed Product.
Second, each Adopter must submit the first product of each Licensed Product type (i.e. source, sink, repeater, or cable) to an HDMI Authorized Testing Center (ATC) for testing. Once an Adopter product of each type has passed testing, it is not required to submit to the ATC subsequent products of that type. However, Adopters must still self-test the products for compliance to the HDMI test specification. For example, once an Adopter's television has passed ATC testing, it is not required to submit another television or other display for ATC testing. However, to help ensure HDMI interoperability, we encourage Adopters to use the ATCs.Return to top
Q. Is HDMI backward compatible with DVI (Digital Visual Interface)?
Yes, HDMI is fully backward compatible with DVI compliant devices. HDMI DTVs will display video received from existing DVI-equipped products, and DVI-equipped TVs will display video from HDMI sources. However, some older PCs with DVI are designed only to support computer monitors, not televisions. Consumers buying a PC with DVI should make sure that it specifically includes support for television formats and not just computer monitors.
Also, consumers may want to confirm that the DVI interface supports High-bandwidth Digital Content Protection (HDCP), as content that requires HDCP copy protection will require that both the HDMI and DVI devices support HDCP to properly view the video content.Return to top
Q. Does HDMI accommodate long cable lengths?
Yes. HDMI technology has been designed to use standard copper cable construction at long lengths. In order to allow cable manufacturers to improve their products through the use of new technologies, HDMI specifies the required performance of a cable but does not specify a maximum cable length. We have seen cables pass "Standard Cable" HDMI compliance testing at lengths of up to a maximum of 10 meters without the use of a repeater. It is not only the cable that factors into how long a cable can successfully carry an HDMI signal, the receiver chip inside the TV or projector also plays a major factor. Receiver chips that include a feature called "cable equalization" are able to compensate for weaker signals thereby extending the potential length of any cable that is used with that device.
With any long run of an HDMI cable, quality manufactured cables can play a significant role in successfully running HDMI over such longer distances.Return to top
Q. How do I run HDMI cables longer than 10 meters?
There are many HDMI Adopters working on HDMI solutions that extend a cable’s effective distance from the typical 10 meter range to much longer lengths. These companies manufacture a variety of solutions that include active cables (active electronics built into cables that boost and extend the cable’s signal), repeaters, amplifiers as well as CAT5/6 and fiber solutions.Return to top
Q. How can I tell if a cable is an HDMI certified cable?
All HDMI products are required to be certified by the manufacturer as part of the HDMI Compliance Test Specification. However, there may be instances where cables bearing the HDMI logo are available but have not been properly tested. HDMI Licensing, LLC actively investigates these instances to ensure that the HDMI trademark is properly used in the market. We recommend that consumers buy their cables from a reputable source and a company that is trusted.Return to top
Q. What is the difference between a “Standard” HDMI cable and a “High-Speed” HDMI cable?
Recently, HDMI Licensing, LLC announced that cables would be tested as Standard or High-Speed cables.
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- Standard (or “category 1”) HDMI cables have been tested to perform at speeds of 75Mhz or up to 2.25Gbps, which is the equivalent of a 720p/1080i signal.
- High Speed (or “category 2”) HDMI cables have been tested to perform at speeds of 340Mhz or up to 10.2Gbps, which is the highest bandwidth currently available over an HDMI cable and can successfully handle 1080p signals including those at increased color depths and/or increased refresh rates from the Source. High-Speed cables are also able to accommodate higher resolution displays, such as WQXGA cinema monitors (resolution of 2560 x 1600).
Q. Where can I find a copy of the Adopted Trademark and Logo Usage Guidelines?
The HDMI Adopted Trademark and Logo Usage Guidelines can by downloaded in the Resources section. (Click here.) This section also includes easy-to-follow how-to guides for working with the HDMI Logo.Return to top
Q. Can I upgrade my existing HDMI equipment to add the newer features?
Currently, there are no provisions for doing such an upgrade. Because of the new enhanced feature set, any such conversion would require hardware and firmware upgrades. If there are such conversions, it would come from the manufacturer. Please check with them directly.Return to top
Q. How can I tell the differences in each version of the HDMI specification?
Download a copy of the most recent specification of HDMI. At the beginning of the document, there is a section called "Revision History." In this section, you can view all of the the changes for each revision of the Specification.Return to top
Q. Where can I get more information on becoming a HDMI Adopter?
On the home page of the www.hdmi.org website is a link to "Becoming an Adopter." Click on that link, and all the information you need, including the Adopter agreements and on-line registration, can be found there.Return to top
Q. What is the difference between DVI and HDMI?
HDMI is DVI with the addition of:
- Audio (up to 8-channels uncompressed)
- Smaller Connector
- Support for YUV Color Space
- CEC (Consumer Electronics Control)
- CEA-861B InfoFrames
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Q. How will HDMI change the way we interface with our entertainment systems?
The most tangible and immediate way that HDMI changes the way we interface with our components is in the set-up. One cable replaces up to 11 analog cables, highly simplifying the setting up of a home theater as well as supporting the aesthetics of new component design with cable simplification.
Next, when the consumer turns on the HDMI-connected system, the video is of higher quality since the signal has been neither compressed nor converted from digital to analog and back.
Lastly, because of the two-way communication capabilities of HDMI, components that are connected via HDMI constantly talk to each other in the background, exchanging key profile information so that content is sent in the best format without the user having to scroll through set-up menus. The HDMI specification also includes the option for manufacturers to include CEC functionality (Consumer Electronics Control), a set of commands that utilizes HDMI’s two- way communication to allow for single remote control of any CEC-enabled devices connected with HDMI. For example, CEC includes one-touch play, so that one touch of play on the DVD will trigger the necessary commands over HDMI for the entire system to power on and auto-configure itself to respond to the command. CEC has a variety of common commands as part of its command set, and manufacturers who implement CEC must do so in a way that ensures that these common command sets interoperate amongst all devices, regardless of manufacturer.
CEC is an optional feature, however, so consumer interested in this functionality must look for CEC in the product feature list. Also, it is important to know that some manufacturers are creating their own proprietary names for their implementation of the CEC command set.Return to top
Q. What are the HDMI-related questions consumers should ask when shopping for a new CE or PC device?
Several questions are key to evaluating HDMI on a CE component.
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- How many inputs/outputs do I need?
- We are seeing more and more inputs and outputs on components as more and more people are connecting with HDMI. It is common to see 3 and 4 inputs on an HDTV – many with one input on the side or front for connecting to game consoles or other portable devices such as digital still cameras or camcorders. Always think about the number of sources and displays (or projectors) that could become part of your home theater system, and make sure the device you are evaluating has the number of inputs and outputs to support your needs over the near and long term.
- For those who have existing systems with one or two inputs, and are finding they need more, there are HDMI switches in the market that switch from multiple inputs (sources) to one output (to your display).
- Think features rather than HDMI version number.
HDMI is constantly evolving to meet the needs of the marketplace. The standard is constantly adding more and more features that manufacturers can implement if they desire. But HDMI does not require manufacturers to implement everything that HDMI can do. HDMI provides a menu of capabilities and allows the manufacturer to choose which of those features make sense for its product line.
As a result, HDMI strongly recommends that consumers look for products with the features they want, rather than the version number of the HDMI components. Version numbers reflect capabilities, but do not correspond to product features. For example, if you want the new video features called Deep Color, look for Deep Color in the feature set rather than HDMI 1.3, the version of the specification that enabled Deep Color. Why? Because the version of the specification that enables Deep Color (1.3) does not mandate that Deep Color functionality be implemented.
However, it is important to also note that all HDMI versions are backwards compatible, so it does not matter what version of HDMI is in the component, all HDMI-enabled components will work together at the highest level of shared functionality.
Q. As more and more devices converge, is HDMI an interface that can accommodate convergence between the PC and CE?
Absolutely. HDMI was developed using the same technology as DVI (Digital Visual Interface), the digital connection standard for the PC environment. So, HDMI is fully compatible with all DVI-enabled PCs (since HDMI offers both audio and video over one cable, and DVI carried only video, DVI-HDMI connectivity requires a separate audio cable).
HDMI enables PCs to deliver premium media content including high definition movies and multi-channel audio formats. HDMI is the only interface enabling connections to both HDTVs and digital PC monitors implementing the DVI and HDMI standards – fully compatible with the hundreds of millions of DVI displays already in the market. Return to top